When I get frisky, my mind forgets how old I am, but my body is quick to remind it. – Anon
Be gentle with your body
The mature body is not as strong or limber as it once was. Spend a little extra time finding comfortable positions where sex does not over stress parts of the body. Further, try not bend your joints to much as this can restrict blood flow and increase the possibility of cramps in the arms and legs. It might be worth while to get a copy of the Kama Sutra to help you explore different positions that do not unduly stress the body.
For example: if the “doggy’ position is a favorite, then try having the lower person laying flat on their stomach. Then take one knee and bend it until the pelvis is rotated to about 90 degrees from the surface. This position gives all the access with much less muscle or joint strain.
NOTE: Mature men regularly complain of cramps during sex. If you can change position so the appendage that is cramping can stretch straight, the cramp with normally go away. Frequently it is possible to do this without interrupting the session.
Where many types of ED can be solved nicely with pills, there are certain types that cannot. For example; if the prostrate or Testicles are physically injured or removed it is virtually impossible for the penis to become erect. Does this mean no-more-sex? No! It just means that you have to focus on having other types of sex, rather than penetrative.
Were some injuries make ejaculation difficult or impossible, this does not have to stop sex. In the male body orgasm and ejaculation are two separate events. Several advance forms of sex, like Tantra, teaches how to have the orgasm without the ejaculation. This type of orgasm can be as, if not more, fulfilling that the standard ejaculation and orgasm combination.